N-type Ag4Sn0. 5S2Te liquid thermoelectric material with low thermal conductivity, and preparation method and application of n-type Ag4Sn0. 5S2Te liquid thermoelectric material

Abstract

The invention discloses an n-type Ag4Sn0. 5S2Te liquid thermoelectric material with low thermal conductivity and a preparation method and application thereof, the chemical formula of the n-type Ag4Sn0. 5S2Te liquid thermoelectric material with low thermal conductivity is Ag4Sn0. 5S2Te, and the n-type Ag4Sn0. 5S2Te liquid thermoelectric material with low thermal conductivity belongs to a # imgabs0 # space group of a cubic system; the chemical formula of the Te vacancy defect of the Ag4Sn0. 5S2Te after thermoelectric performance optimization is Ag4Sn0. 5S2Te < 0.92 >; according to the n-type Ag4Sn0. 5S2Te liquid thermoelectric material with low thermal conductivity, an anion rigid frame is formed by a SnS4 tetrahedron element at the edge center and Te at the face center position, and Ag ions move in the anion rigid frame; according to the method, the material Ag4Sn0. 5S2Te is synthesized through a high-temperature vacuum solid-phase method, the ultralow heat conductivity of 0.22-0.32 Wm <-1 > K <-1 > is achieved at 300-823 K, the material is a consistent molten compound and keeps a stable cubic phase at 200-1100 K, and the thermoelectric figure of merit of 0.74 is achieved through Te vacancy defect regulation and control and Ag4Sn0. 5S2Te0. 92 and is improved by 95% compared with intrinsic thermoelectric figure of merit of 0.74.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and specifically relates to an n-type Ag with low thermal conductivity. 4 Sn 0.5 S 2 Te-based liquid thermoelectric materials and their preparation methods and applications. Background Art

[0002] Thermoelectric devices can achieve direct conversion between thermal energy and electrical energy. The energy conversion efficiency of the device is calculated by the dimensionless thermoelectric figure of merit ZT = S 2 σT / κ tot To determine, where S is the Seebeck coefficient, σ is the conductivity, T is the absolute temperature, κ tot (κ tot =κ ele +κ lat ) is the thermal conductivity, including the electronic thermal conductivity (κ ele ) and lattice thermal conductivity (κ lat Obviously, high power factor PF (S 2 σ) and low κ tot It is the key to obtain a high ZT value.

[0003] Based on the concept of "phononic liquid-electron crystal (PLEC), Ag-based argyrodite liquid materials have intrinsic ultra-low κ lat Compared with the traditional liquid-like material Cu 2-y X, Ag 2 X (X = S, Se and Te), has become a new type of high-performance material. This type of material contains a large number of atoms in the unit cell, Ag + High fluidity and strong anharmonicity lead to intrinsic ultra-low κ lat At the same time, the rigid anion framework with covalent bonds ensures the transport of carriers, similar to classical traditional semiconductors. These two functional characteristics can achieve independent regulation of electrical and thermal transport. However, as the temperature rises, the traditional argyrodite material will transform from a low-temperature ordered phase to a disordered cubic phase. Therefore, in order for the device to serve for a long time at high temperatures, finding a new thermoelectric material with a stable structure and no phase change in the test temperature range is an important issue that needs to be solved now. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes an n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 Te-based liquid thermoelectric materials and their preparation methods and applications.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] An n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 Te-based liquid thermoelectric material, the n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 The chemical formula of Te-based liquid thermoelectric materials is Ag 4 Sn 0.5 S 2 Te, belongs to the cubic system, Space group; Ag 4 Sn 0.5 S 2 The chemical formula of Te vacancy defect created by thermoelectric performance optimization is Ag. 4 Sn 0.5 S 2 Te 0.92 ; The n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 Te-based liquid thermoelectric materials are composed of SnS 4 The tetrahedral unit and Te at the face-center position constitute a rigid framework of the anion, and the Ag ions move within the rigid framework of the anion.

[0007] Preferably, the n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 The unit cell parameters of Te-based liquid thermoelectric materials are: α=β=γ=90°,Z=6,unit cell volume

[0008] Preferably, the n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 Te-type liquid thermoelectric materials have ultra-low thermal conductivity at 300-823K, with a thermal conductivity of 0.22-0.32Wm -1 K -1 , is a consistent melting compound; the n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 Te-based liquid thermoelectric materials maintain a stable cubic phase at 200-1100K.

[0009] An n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 The preparation method of Te-based liquid thermoelectric material specifically comprises the following steps:

[0010] S1. Prepare raw materials Ag particles, Sn particles, S particles and Te particles;

[0011] S2. Preparation of millimeter-scale single crystals: weigh 0.5 g of each of Ag, Sn, S and Te in molar ratio and place them in a quartz glass tube. -5 -10 -1 The quartz tube was sealed with an oxyhydrogen flame under the condition of 1.5 Pa, and then sintered by vacuum solid phase method;

[0012] Preparation of polycrystalline ingot: weigh 6 g of Ag, Sn, S and Te in molar ratio, put them into a quartz glass tube, and place them in a vacuum tube at 10 -5 -10 -1 The quartz tube is sealed with an oxyhydrogen flame under the condition of Pa, and then sintered by vacuum melting method;

[0013] S3, grinding the single crystal block sample obtained after spontaneous crystallization in step S2 to obtain a millimeter-level single crystal; grinding the polycrystalline ingot sample obtained in step S2, and then sintering it with spark plasma to obtain an n-type Ag with low thermal conductivity. 4 Sn 0.5 S 2 Te-based liquid thermoelectric materials.

[0014] Preferably, in step S2, the purity of the single substances Ag, Sn, S and Te is greater than 99%.

[0015] Preferably, in step S2, the specific process of the millimeter-scale single crystal reaction is: uniformly heating from room temperature to 1000-1150°C for 20-25 hours, keeping warm for 3-7 days, and then cooling to room temperature at a cooling rate of 2-7°C / h to obtain a millimeter-scale single crystal; the specific process of the polycrystalline ingot reaction is: heating to 1000°C at a heating rate of 40-80°C / h for 16 hours, keeping warm for 2 days, and quenching in ice water to obtain Ag 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 The compound was heated at 550°C for 5 days.

[0016] Preferably, in step S3, the sintering temperature of spark plasma sintering is 500-600° C., the sintering time is 15-40 min, and the sintering pressure is 40-60 MPa.

[0017] Preferably, in step S3, the sintering time of spark plasma sintering is 37 minutes; and the rate of heating to the sintering temperature is 50-100° C. / min.

[0018] An n-type Ag with low thermal conductivity4 Sn 0.5 S 2 Application of Te-based liquid thermoelectric materials, the n-type Ag with low thermal conductivity 4 Sn 0.5 S 2 Te-type liquid thermoelectric materials are used as thermoelectric materials in the field of new energy.

[0019] After adopting the above technical scheme, the present invention has the following beneficial effects: the synthesis method of the present invention has simple steps and is easy to operate, and can prepare millimeter-level single crystal samples; the Ag synthesized by the present invention 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 , with 0.22-0.32W m at 300-823K -1 K -1 The material is a uniformly molten compound that maintains a stable cubic phase at 200-1100K and is regulated by Te vacancy defects. 4 Sn 0.5 S 2 Te 0.92 A thermoelectric figure of merit of up to 0.74 was achieved, which is 95% higher than the intrinsic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Ag prepared in Example 1 of the present invention 4 Sn 0.5 S 2 Unit cell structure diagram of Te;

[0021] Figure 2 Ag prepared in Example 1 of the present invention 4 Sn 0.5 S 2 Millimeter-scale single crystals of Te;

[0022] Figure 3 Ag prepared in Example 1 of the present invention 4 Sn 0.5 S 2 DSC curve of Te;

[0023] Figure 4 Ag prepared in Example 1 of the present invention 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Powder X-ray diffraction pattern of

[0024] Figure 5 Ag prepared in Example 1 of the present invention 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Plot of conductivity as a function of temperature;

[0025] Figure 6 Ag prepared in Example 1 of the present invention 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Diagram of thermoelectric potential as a function of temperature;

[0026] Figure 7 Ag prepared in Example 1 of the present invention 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Plot of thermal conductivity as a function of temperature;

[0027] Figure 8 Ag prepared in Example 1 of the present invention 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Thermoelectric figure of merit diagram as a function of temperature. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Prepare raw materials Ag particles, Sn particles, S particles and Te particles. Among them, the purity of Ag particles is 99.99% (produced by Hebei Luohong Technology Co., Ltd.), the purity of Sn particles is 99.99% (produced by Hebei Luohong Technology Co., Ltd.), the purity of S particles is 99.999% (produced by Hebei Luohong Technology Co., Ltd.) and the purity of Te particles is 99.99% (produced by Hebei Luohong Technology Co., Ltd.).

[0030] like Figures 1 to 8 shown.

[0031] Example 1: Ag 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Preparation

[0032] 1) Weigh the single elements Ag, Sn, S and Te according to the molar ratio, put them into a quartz glass tube, and place them under vacuum at 10 -3 Pa, and then the quartz tube was sealed with a hydrogen-oxygen flame;

[0033] 2) placing the sealed vacuum quartz tube in step 1) in a muffle furnace for solid phase reaction. The reaction conditions for the millimeter-scale single crystal are: uniformly raising the temperature from room temperature to 1000°C for 20 hours, keeping it at 1000°C for 3 days, and slowly cooling it down to room temperature at a rate of 5°C / h. The reaction conditions for the polycrystalline powder are: uniformly raising the temperature from room temperature to 1000°C for 16 hours, keeping it at 1000°C for 2 days, quenching with ice water, and keeping it at 550°C for 5 days;

[0034] 3) Step 2) After spontaneous crystallization, a millimeter-sized single crystal is obtained. The ingot obtained by ice water quenching is fully ground and then subjected to spark plasma sintering. The sintering temperature of the spark plasma sintering is 550°C, the sintering time is 37min, and the sintering pressure is 45Mpa to obtain n-type Ag with low thermal conductivity. 4 Sn 0.5 S 2 Te-based liquid thermoelectric materials.

[0035] Example 2: Ag 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Preparation

[0036] 1) Weigh the single elements Ag, Sn, S and Te respectively according to mole, and put them into a quartz glass tube, and place them under vacuum degree of 10 -2 Pa, and then the quartz tube was sealed with a hydrogen-oxygen flame;

[0037] 2) The sealed vacuum quartz tube in step 1) is placed in a muffle furnace for solid phase reaction. The reaction conditions for the millimeter-scale single crystal are to uniformly increase the temperature from room temperature to 1050°C for 22 hours, keep it at 1000°C for 3 days, and slowly cool it down to room temperature at a rate of 5°C / h. The reaction conditions for the polycrystalline powder are to uniformly increase the temperature from room temperature to 1000°C for 16 hours, keep it at 1000°C for 2 days, and quench it in ice water to obtain Ag. 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 The compound was heated at 550°C for 5 days.

[0038] 3) Step 2) After spontaneous crystallization, a millimeter-sized single crystal is obtained. The ingot obtained by ice water quenching is fully ground and then subjected to spark plasma sintering. The sintering temperature of the spark plasma sintering is 550°C, the sintering time is 37min, and the sintering pressure is 45Mpa to obtain n-type Ag with low thermal conductivity. 4 Sn 0.5 S 2 Te-based liquid thermoelectric materials.

[0039] Example 3: Ag 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Preparation

[0040] 1) Weigh the single elements Ag, Sn, S and Te according to the molar ratio, and put them into a quartz glass tube, and place them under a vacuum degree of 10 -1 Pa, and then the quartz tube was sealed with a hydrogen-oxygen flame;

[0041] 2) The sealed vacuum quartz tube in step 1) is placed in a muffle furnace for solid phase reaction. The reaction conditions for the millimeter-scale single crystal are to uniformly increase the temperature from room temperature to 1100°C for 25 hours, keep it at 1100°C for 3 days, and slowly cool it down to room temperature at a rate of 5°C / h. The reaction conditions for the polycrystalline powder are to uniformly increase the temperature from room temperature to 1000°C for 16 hours, keep it at 1000°C for 2 days, and quench it in ice water to obtain Ag 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 The compound was heated at 550°C for 5 days.

[0042] 3) Step 2) After spontaneous crystallization, a millimeter-sized single crystal is obtained. The ingot obtained by ice water quenching is fully ground and then subjected to spark plasma sintering. The sintering temperature of the spark plasma sintering is 550°C, the sintering time is 37min, and the sintering pressure is 45Mpa to obtain n-type Ag with low thermal conductivity. 4 Sn 0.5 S 2 Te-based liquid thermoelectric materials.

[0043] Performance Testing:

[0044] 1) First weigh 0.5g of Ag 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 The compound (prepared in Example 1) was then ground into a powder sample using an agate mortar and subjected to powder X-ray diffraction analysis. The analysis results are shown in FIG. Figure 4 The test angle is 10-70 degrees, and the X-ray diffraction peaks of the prepared samples are completely consistent with the calculated peaks, and no impurity phase is observed.

[0045] 2) The Ag prepared in Example 1 was tested using the thermoelectric material testing system CTA of the domestic company Corio. 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 The electrical properties of the compound are tested. The relationship between conductivity and thermoelectric potential coefficient with temperature, such as Figure 5 and Figure 6 As shown. 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 The conductivity of the compound increases with the increase of temperature. As the number of Te vacancies increases, the conductivity increases. At 823K, Ag 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 The conductivity is 8.29Scm -1 and 31.82S cm -1 The prepared Ag 4 Sn0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 The absolute value of the compound's thermoelectric potential increases first and then decreases with increasing temperature. At 576K and 691K, Ag 4 Sn 0.5 S 2 The maximum peak value of Te's thermoelectric potential at 576K is -446μVK -1 , Ag 4 Sn 0.5 S 2 Te 0.92 The maximum peak value of the thermoelectric potential at 691K is -329μV K -1 .

[0046] 3) The thermal diffusion coefficient D of the material prepared in Example 1 was tested using a laser flash thermal conductivity meter LFA467 from NETZSCH, Germany. The thermal conductivity was calculated by κ = C p Dρ is calculated, density ρ is obtained by Archimedes drainage method, specific heat C p It is calculated by the Dulong-Petit formula. The relationship between thermal conductivity and temperature is as follows Figure 7 As shown in Figure 2, the thermal conductivity of the sample has no dependence on temperature. 4 Sn 0.5 S 2 Te and Ag 4 Sn 0.5 S 2 Te 0.92 Ultra-low thermal conductivity 0.22-0.32Wm at 300-823K -1 K -1 .

[0047] 4) The Ag prepared in Example 1 4 Sn 0.5 S 2 Te compound was ground into powder, 5-10 mg was taken and placed in a Φ4mm×2mm quartz glass crucible, and a blank quartz glass crucible was placed as a reference. A HCT-2 (HENVEN) thermal analyzer was used to perform DSC analysis on the material prepared in Example 1 at a heating rate of 10°C / min to obtain the following curve: Figure 3 As shown. According to the DSC test results, Ag 4 Sn 0.5 S 2 The melting point of Te compounds is 1170K and the crystallization point is 1142K.

[0048] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A n-type Ag4Sn with low thermal conductivity 0.5 S2Te-based liquid thermoelectric material, characterized by: The n-type Ag4Sn with low thermal conductivity 0.5 The chemical formula of S2Te-type liquid thermoelectric material is Ag4Sn 0.5 S2Te, belongs to the cubic system, Space group: Ag4Sn 0.5 The chemical formula of the Te vacancy defect in S2Te after thermoelectric performance optimization is Ag4Sn 0.5 S2T 0.92 ; The n-type Ag4Sn with low thermal conductivity 0.5 S2Te-type liquid thermoelectric materials are composed of SnS4 tetrahedral units at the edge centers and Te at the face centers to form an anion rigid framework, in which Ag ions move.

2. The n-type Ag4Sn with low thermal conductivity as claimed in claim 1 0.5 S2Te-based liquid thermoelectric material, characterized in that: The n-type Ag4Sn with low thermal conductivity 0.5 The unit cell parameters of S2Te-type liquid thermoelectric materials are: α=β=γ=90°,Z=6,unit cell volume 3. The n-type Ag4Sn with low thermal conductivity as claimed in claim 1 0.5 S2Te-based liquid thermoelectric material, characterized by: The n-type Ag4Sn with low thermal conductivity 0.5 S2Te-like liquid thermoelectric materials have ultra-low thermal conductivity at 300-823K, with a thermal conductivity of 0.22-0.32Wm -1 K -1 , is a consistent melting compound; the n-type Ag4Sn with low thermal conductivity 0.5 S2Te-like liquid thermoelectric materials maintain a stable cubic phase at 200-1100K.

4. An n-type Ag4Sn with low thermal conductivity as claimed in any one of claims 1 to 3 0.5 The preparation method of S2Te type liquid thermoelectric material is characterized in that: The specific steps include: S1. Prepare raw materials Ag particles, Sn particles, S particles and Te particles; S2. Preparation of millimeter-scale single crystals: weigh 0.5 g of each of Ag, Sn, S and Te in molar ratio and place them in a quartz glass tube. -5 -10 -1 The quartz tube was sealed with an oxyhydrogen flame under the condition of 1.5 Pa, and then sintered by vacuum solid phase method; Preparation of polycrystalline ingot: weigh 6 g of Ag, Sn, S and Te in molar ratio, put them into a quartz glass tube, and place them in a vacuum tube at 10 -5 -10 -1 The quartz tube is sealed with an oxyhydrogen flame under the condition of Pa, and then sintered by vacuum melting method; S3, grinding the single crystal block sample obtained after spontaneous crystallization in step S2 to obtain a millimeter-level single crystal; grinding the polycrystalline ingot sample obtained in step S2, and then sintering it with spark plasma to obtain an n-type Ag4Sn with low thermal conductivity. 0.5 S2Te-type liquid thermoelectric materials.

5. The n-type Ag4Sn with low thermal conductivity as claimed in claim 4 0.5 The preparation method of S2Te type liquid thermoelectric material is characterized by: In step S2, the purity of the single substances Ag, Sn, S and Te is greater than 99%.

6. An n-type Ag4Sn with low thermal conductivity as claimed in claim 4 0.5 The preparation method of S2Te type liquid thermoelectric material is characterized in that: In step S2, the specific process of the millimeter-scale single crystal reaction is: uniformly heating from room temperature to 1000-1150°C for 20-25 hours, keeping warm for 3-7 days, and then cooling down to room temperature at a cooling rate of 2-7°C / h to obtain a millimeter-scale single crystal; the specific process of the polycrystalline ingot reaction is: heating to 1000°C at a heating rate of 40-80°C / h for 16 hours, keeping warm for 2 days, and quenching in ice water to obtain Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2T 0.92 The compound was heated at 550°C for 5 days.

7. The n-type Ag4Sn with low thermal conductivity as claimed in claim 4 0.5 The preparation method of S2Te type liquid thermoelectric material is characterized by: In step S3, the sintering temperature of the spark plasma sintering is 500-600° C., the sintering time is 15-40 min, and the sintering pressure is 40-60 MPa.

8. An n-type Ag4Sn with low thermal conductivity as claimed in claim 7 0.5 The preparation method of S2Te type liquid thermoelectric material is characterized by: In step S3, the sintering time of spark plasma sintering is 37 minutes; the rate of heating to the sintering temperature is 50-100°C / min.

9. An n-type Ag4Sn with low thermal conductivity as claimed in any one of claims 1 to 3 0.5 The application of S2Te-type liquid thermoelectric materials is characterized by: The n-type Ag4Sn with low thermal conductivity 0.5 S2Te-type liquid thermoelectric materials are used as thermoelectric materials in the field of new energy.

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